The aim of this study was to determine the risk factors associated with tuberculosis among human immunodeficiency virus (HIV)-infected persons living in Switzerland, a country with low prevalence of tuberculous infection. We performed a nested case-control study and logistic regression. Cases (n = 239) were patients participating in the Swiss-HIV Cohort study (n = 7,103), diagnosed with bacteriologically confirmed tuberculosis. The rest of the cohort population was used as control. Patients from industrialized countries had a risk of tuberculosis similar to those from Switzerland (adjusted odds ratio (OR) 1.1; 95% confidence interval (95% CI) 0.7-1.5); whereas the risk among patients from Eastern Europe (OR 2.8, 95% CI 1.9-3.7), Brazil (OR 10.6; 95% CI 9.6-11.5), and Africa (OR 3.0; 95% CI 2.4-3.6) was markedly higher. Immune suppression, as indicated by low CD4 + cell count, was an independent risk factor for tuberculosis (OR 7.8; 95% CI 7.3-8.3 for patients with CD4 + < 50 cells.mm-3 compared to those with CD4 + > 500 cells.mm-3). Age, sex and HIV-transmission category did not appear to increase the risk of tuberculosis after adjustment for other patient characteristics. In conclusion, in countries of low prevalence of Mycobacterium tuberculosis infection, to originate from a country with high prevalence of tuberculosis infection and to have advanced immunodeficiency are significant risk factors for tuberculosis. They may be used to complement the tuberculin skin test in targeting patients for preventive chemotherapy.